The twins, identified only as Fernando and Fabricio, tried to shirk responsibility for the newborn as DNA tests came back inconclusive, reports The Sun.
The mystifying results are said to have failed to provide a solid answer because the men are so genetically similar.
Each brother tried to blame the other, Brazilian news outlet Globo reports.
But a judge ruled they were denying the innocent child a right to know her biological dad.
District judge Filipe Luis Peruca, at the Cachoeira Alta Court in the central state of Goias, said both brothers must be included on the girl’s birth certificate.
The ruling forces both men to pay maintenance of 30 per cent of the minimum wage — 230 reais ($AU84) a month.
Luckily for the tot this means she will get twice as much as other children from the same economic background.